eCPM is a useful way for publishers to compare revenue across different advertising programs. It is calculated by dividing total earnings by the number of impressions in thousands.

When a publisher earns $400 from 20,000 impressions, then the eCPM is $2 ($400 divided by 200)

For small sites with impressions less then 1000 the eCPM is calculated in another way. Suppose your ad program receives 400 page impressions and $2.00 in total earnings. The eCPM is $5 ($2 divided by 400 times 1000).

Note 1:
The small site generates more revenue per impression compared to the larger site.

Note 2:
M is the Roman numeral for thousand.

EPC

Earnings Per Click

It is calculated by dividing the total earnings from clickthroughs by the number of clicks.

When you earn $200 by clickthroughs and the total number of clicks is 1,000, then the EPC is 0.20 ($200 divided by 1,000).

hit

A hit is a successful request to the web server from a visitor browser for any type of file, whether an HTML page, image or any other type. A single web page can cause many hits one for each image included on the page, etc.

An advertising model in which advertisers pay for clickthroughs to their website. Ads are served based on keywords or themes.

publisher

In the online advertising world a publisher is a person/company with a high traffic website who wants to generate revenue by placing ads from advertisers on the site.

session

A session is defined as a series of clicks on your site by an individual visitor during a specific period of time. A session is initiated when the visitor arrives at your site, and it ends when the browser is closed or there is a period of inactivity.

Example:
When a visitor opens a browser and vists a web page on site A then this is a session. If the visitor stays on site A clicking on several pages and even clicking on the same page, it is still the same session.

When the vistor is going to site B and returns back to site A then a new session is created.

When the vistor is on site A, closes and starts the browser and vists site A again, then a new session is also created.

SERP

A search engine results page, or SERP, is the listing of web pages returned by a search engine in response to a keyword query.

unique visitor

When a visitor visits a site it is counted as an unique vistor. Multiple repeat visits are not counted based on the visitor ip address.